RIA Novosti – NASA said on Tuesday that it is struggling to determine what caused more than a liter of water to pour into the helmet and suit of an Italian astronaut during a spacewalk Tuesday outside the International Space Station (ISS), prompting the US space agency to abort the spacewalk out of concern for the safety of the crew.

“Today was certainly a very serious issue… Choking or drowning was a definite possibility” in a situation like this, said Karina Eversley, lead spacewalk officer, during an afternoon NASA press conference.

European Space Agency (ESA) astronaut Luca Parmitano reported feeling “a lot of water” on the back of his head when he and US flight engineer Chris Cassidy were about an hour into a planned six hour spacewalk, during which they were supposed to prepare the orbital outpost for a new Russian laboratory module set to arrive later this year and conduct other maintenance tasks.

The water eventually got into Parmitano’s eyes and drenched his nose and mouth.

Mission Control at the Johnson Space Center in Houston decided to abruptly end the spacewalk, even though “the water was not an immediate health hazard for Parmitano,” NASA said. NASA engineers “do not have any cause for the leak at this point,” spokesman Rob Navias told RIA Novosti.

The aborted spacewalk was the second shortest in ISS history. The record for the shortest ISS spacewalk belongs to US astronaut Mike Fincke, who in 2004 was outside the space station for just 14 minutes when a pressure sensor problem was detected in his Russian space suit.

After returning to the airlock of the space station Tuesday, Parmitano had to be helped by other ISS crew members to quickly remove his spacesuit.

“We have not seen a problem like this before with this accumulation of water,” said Eversley.

NASA officials said they don’t believe his drinking water was related to the leak. The other possible cause might be a problem with the cooling system for the spacesuit, but officials stressed at this point they haven’t determined the source of the problem.

Tuesday’s spacewalk was Parmitano’s second and Cassidy’s sixth trip outside the ISS. The two were supposed to prepare for the arrival of the new Russian lab, replace a video camera, relocate wireless television camera equipment, troubleshoot a problem with a cover over electronic relay boxes on the space station’s truss, and reconfigure thermal insulation over a failed electronics box that was removed from the station’s truss last year.

None of the tasks that Cassidy and Parmitano were scheduled to do during the spacewalk were urgent or vital to the safety of the crew on board the ISS, NASA said.